I get dumbfounded when bicyclists think they have the answer to creating a low-carbon environment.
We know their strong points. Bicycles operate on human food power; the cyclist's respiration generates CO2, and a bit of methane out the other end, and the cyclist would do some of that even if not on a bike, so the CO2 footprint is only a bit more due to exercise. The energy it takes to manufacture a bicycle is much less than for a car, yet some bike frames can last as long as a car. More bikes can fit on a patch of roadway than the car equivalents with passengers. All good stuff.
That said, bicyclists today seldom reflect on the historic 20th century political and economic struggle to establish smooth surfaces for their rubber-wheeled travel. The asphalt roads are a product of the petroleum industry. The concrete roads and bridges with their concrete, structural steel and rebar, are carbon-intensive to make. And repair.
To fully imagine a post-fossil fuel future, take out the smooth black roads and concrete overpasses, take out the steel-trussed bridges and the diesel-powered ferries.
Think about compacted dirt lanes, cobblestone roads, and a ferry operated by wind, or maybe by rechargeable electric engines.
The electric car and the bike are both rides taken on the waning of fossil fuel.